Since the filename itself doesn't describe the video, you can:
: Right-click the file → Properties → Details (Windows) to see if there is a contributing artist or original title. 1_5021547738098041451mp4
: Search your "Saved Messages" or recent chats for "5021547738098041451" to find the original message. Since the filename itself doesn't describe the video,
The filename "1_5021547738098041451mp4" follows the specific naming convention used by for downloaded media files. 1_5021547738098041451mp4
While I cannot access the specific video file stored on your device or within a private Telegram chat, here is the context for that file type: File Breakdown : Telegram messenger (Desktop or Mobile). Format : MP4 (standard video file).
: You likely found this in your Telegram Desktop or Telegram Video folder.